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1.方法理論在氨性溶液中,镍离子与乙二胺四乙酸二鈉(簡称EDTA)和紫脲酸銨生成稳定的可溶性絡合物。但由于二者稳定性不同(NiY~(-2),PK=18.4;NIR~+,PK_3=10,9),故在同一种溶液中若有上述三种离子,先生成NiY~(-2),多余的Ni~(++)才和紫脲酸銨生成絡盐。紫脲酸銨同镍离子所生成絡合物的顔色是淡黄色,游离紫脲酸铵呈紫色,因此,可以在溶液中預先加入紫脲酸銨,然后用标准EDTA溶液滴定。終点为游离紫脲酸銨顔色。
1. Methodology In ammoniacal solution, nickel ion and ethylenediaminetetraacetic acid disodium (referred to as EDTA) and ammonium urea to generate stable soluble complexes. However, due to the different stability (NiY ~ (-2), PK = 18.4; NIR ~ +, PK_3 = 10,9), so if the above three ions in the same solution, ), Excess Ni ~ (++) and ammonium salt of urea formation of complex salt. The color of the complex formed by ammonium urethane with nickel ions is light yellow and the free ammonium ureas are purple so that ammonium thiocyanurate can be pre-added to the solution and titrated with a standard EDTA solution. The endpoint is free ammonium oxalate color.